The present invention relates to a method of manufacturing a magnetic recording medium, more particularly to a method of manufacturing a magnetic recording medium comprising magnetic powder, and a binding agent mainly comprising vinyl chloride resin.
In recent years, the capacity of a magnetic recording medium is becoming larger and larger. For a coating type magnetic recording medium, there have been various methods adopted for improving the recording capacity; some is to extend a full length of a magnetic tape as a magnetic recording medium and another is to provide such an improved recording system as to narrow track pitches or to shorten wave length for recording. Among those methods, a method of adopting a shortened wave length for recording requires a high density of recording and a high output for the recording medium, for which a magnetic powder having a higher coercive force and a higher magnetic flux density is used for the magnetic layer of the object magnetic tape. Thus, the magnetic powder becomes further needle-like and fine in structure.
One of the conditions for manufacturing magnetic tape having favorable recording and reproducing properties is to disperse magnetic powder sufficiently in a magnetic coating material. However, the above fine magnetic powder has large cohesive force, so that it is difficult to disperse aggregate of such a fine magnetic powder using the related art method that uses conventional binding agent, dispersing agent, etc. With a magnetic tape thus manufactured with such fine magnetic powder using the related art method, the required and expected magnetostatic property and electromagnetic conversion property cannot be satisfied due to insufficient dispersion of the magnetic powder.
Under such circumstances, it is an object of this invention to provide a method of manufacturing a magnetic recording medium, which can disperse needle-like and fine magnetic powder sufficiently to realize higher density recording.